Electromagnetic apparatus



March 3, 1942. TRQMBETTA 2,275,115

ELECTROMAGNETIC APPARATUS Filed Feb. 29, 1940 2 Sheets$heet 2 .INVENTOR.

- in construction,

Patented 3, 1942 UNlTED STATES PATENT OFFICE 2,275.1, ELECTROMAGNETIC APPARATUS Paniilo 'lrombetta, Milwaukee, Wis.

Application February 29. iatasemi No. 321,528

4 Claims.

' my application for U. S. Letters Patent, Serial No.

738,571, filed August 6, 1934, and of my application for U. 8. Letters Patent, Serial No. 177,772, filed December 2, 1937.

The principal object of the invention is to provide an alternating current magnet which has a greater capacity for its size, and which is simple compact, and economical to manufacture.

Another objectof the invention is to provide an improved construction for the magnetic circuit of a solenoid.

Another object is to provide an improved casing for a solenoid, the casing being of simple construction for quick assembly and mounting of the solenoid.

Other objects of the invention will be set forth hereinafter in connection with the description of the preferred embodiment illustrated in the accompanying drawings.

In the drawings:

Figure l is a side elevation of a solenoid embodying the invention, partly in section;

Fig. 2 is a top plan view of the solenoid;

Fig. 3 is a transverse vertical section taken on line 3-3 of Fig. l; I

Fig. 4 is a side elevation of the top section of the casing;

Fig. 5 is a side elevation of the bottom section of the casing; I Fig. 6 is a side elevation of a modified form of solenoid partly in section similar to Fig. 1;-

Fig. 7 is a perspective view of the parts in position for assembly of the solenoid shown in Fig. 6; and

Fig. 8 is a section taken on line of Fig. 6.

In manufacturing small solenoids for alternating current it has been found best to construct the plunger or core of laminations of highly permeable metal, while the outer casing part of the flux path may be constructed of non-laminated parts of larger cross'sectional area providing a larger heat radiating surface and a lower flux density.

The solenoid illustrated in Figs. 1 to 5, inclusive, comprises a coil assembly I, a casing assembly 2 and a laminated core or plunger 3.

The coil assembly i comprises the winding 4 on a spool which is constructed of the inner tube 5,

an upper plate I and a bottom plate I. The tube 6 extends through openings in the plates 6 and l and has its upper end extend upwardly beyond the top plate 8 and its lower end flush with the lower surface of the bottom plate I. The tube 5 is non-circular, and preferably rectangular, in

cross section for receiving the laminated plunger or core 3 which is of complemental cross section.

The casing assembly is more particularly illustrated in Figures 4 and 5. The upper section illustrated in Fig. 4 is formed of an inverted U- shaped piece 3 of flat top and straight sides at right angle thereto pressed from a flat sheet of metal and an upper plate 9 secured on top of the .same with its edges extending beyond the sides of the piece 3 a distance equal approximately to the thickness of the sheet metal stock. A central rectangular opening I0 is provided in the piece 3 and in the plate 9 for receiving the tube 5 of the coil, and plate 8 has its edges adjacent the opening ill turned upwardly as at Ii to bear against the tightly fit the tube 5 and provide for greater area of contact for transference of flux.

The bottom section of the casing, shown in Fig. 5, is formed of a U-shaped piece I! of flat bottom and straight sides at right angles thereto, and a plate i3 secured inside the piece I 2 and coextensive with the flat bottom thereof. A pole piece It of solid highly permeable metal of the same cross section as core 3 is preferably secured tothe center of plate l3 for extending into the lower end of tube 5 and providing a more uniform power curve for the solenoid through the normal range of movement of the plunger 3. The pole piece may, however, be eliminated, in which case the plunger 3 would extend through the coil and into contact with the U-shaped piece II, as shown in Figs. 6 to 8.

The piece I! has its upstanding sides spaced at distance Just suflicient to receive the depending of the plate 0. Similarly the plate I3 may be made longer and have one or both ends bent upwardly along the side pieces 12, in which case the sides 8 of the upper piece will be shorter to just meet the edge of the plate l3. However, in each instance it is advisable to have the side walls of each member overlap for a sufllcient distance to facilitate the simple securing of the same together by the screws l5.

In assembling the solenoid the coil assembly I is placed in the upper section of casing 2 with the tube extending through the flanged opening of plate 9 and the whole is then telescoped into the lower section of casing 2. Screws l3 secure the sides of piece l2 to the sides of piece 3, thereby securing all parts in place. The core 3 is then inserted in tube 5.

The construction of the core 3 is of laminations of highly permeable magnetic material suitably assembled and riveted together with insulation therebetween. All laminations are of the same length and width, the plunger preferably being wider than it is thick. A hole i6 in the upper end of the plunger provides for a connection to a mechanism to be controlled by the longitudinal movement of the plunger.

The core 3 may be provided with a suitable pole shading coil, and where the pole piece H is laminated it may likewise be provided with a suitable pole shading coil.

In the construction of the solenoid the laminations of the plunger 3 are arranged to extend at right angles to the sides of the casing, as distinguished from being inplanes parallel thereto. By this means the fiux in each lamination is readily transmitted to the outer casing flux path without having to pass through other laminations.

The solenoid may be mounted by means of the screws l5 or threaded holes ll may be provided in the bottom of the casing for receiving attaching screws.

The modified form of solenoid illustrated in Figures 6 and 7 has its casing formed of two U- shaped members 18 and IS, the former having very short upstanding sides 23 and being adapted to fit the latter with the sides 20 in engagement with the sides 2| of the latter. The sides 20 are secured to the sides 2| by screws 22 at the top of the structure.

The central tube 23 of the spool of winding 24 r is held at its ends by plates 25 and 26 through which it passes. The tube 23 extends upwardly through an opening 21 in the upper member I8 which prevents lateral displacement. Other mean of holding the coil from lateral displacement may be employed.

In this construction, suitable for the smaller solenoids, the outer casing is only of a single thickness at the sides for providing the path for magnetic flux, while in the construction of Figs. 1 to 5 the outer casing was of double thickness on the sides. Furthermore the pole piece It is preferably eliminated and the plunger 28 extended directly to the bottom wall of the casing. This greatly simplifies the construction and provides a more direct path for the flux.

In all of the constructions the casing parts as well as the plunger and pole pieces. are constructed of a metal such as soft iron which is highly permeable by magnetic flux. The sleeve and end plates constituting the spool for the winding are preferably constructed of some relatively non-permeable material. For simplicity of manufacture, it is preferable to employ sheet metal for making the casing since it is usually cheaper and more-reliable in performance.

The laminations ,or parts of the outer casing are of thicker sheets than the laminations of the plunger. By this design a maximum of the eddy current losses is obtained in the casing which is readily cooled by the large surface for radiation, while a minimum of eddy current losses is obtained in the plunger. The non-circular and oblong cross section of the plunger and of the coil tube 5 and 23 insure that the plunger will be assembled with its laminations extending in the right direction relative to the casing and the user cannot change this relation of the parts.

Various embodiments of the invention may be employed within the scope of the claims.

The invention is claimed as follows:

1. In an electro-magnet of the class described, a magnet coil, a frame around the coil forming an outer path for the flux and comprising a U- shaped sheet metal member having an extra plate of metal of substantially the same thickness attached on the flat bottom thereof and coextensive with the bottom, the sides of the member being spaced a distance to accommodate the magnet coil, and an inverted U-shaped sheet metal member having an extra plate of metal of substantially the same thickness attached on the flat upper web of the member, the sides of said second member being spaced to be telescoped within the sides of said first member and shorter to engage said extra plate on the bottom member while the sides of the latter extend upwardly to engage theplate on the top member to provide a frame of substantially uniform double thickness and cross section throughout the flux path, the magnet coil having an opening therein for receiving an armature core, and the frame having an opening axially aligned with the opening in the coil for additionally receiving said armature core.

2. In an eleotro-magnet of the class described, a frame surrounding a magnet winding to form an outer path for the flux and comprising a U- shaped sheet metal member formed from two overlapping sheets of different lengths, a second U-shaped sheet metal member formed from two overlapping sheets of different lengths, the legs of one member being disposed in eomplemental overlapping relation with those of the other member, the ends of each sheet of each member engaging a sheet of the other member adjacent its ends to provide a substantially double wall frame having a space between the members for the magnet winding, and one of said members having an opening through its center for receiving a movable plunger disposed axially of the a double wall frame having a space between the members for the magnet winding, one of said members having an opening through its center for receiving the core, said core and opening being of complemental non-circular cross section meable material to provide a flux path of-hlgh 10 capacity and low heat loss, and an outer frame member of relatively thick sheet metal of a width approximately as great as the diameter 0! the winding, encircling the winding in the plane of the laminations of the plunger and having an opening at one end for receiving the plunger,

said frame having a large surface area and being disposed with its plane surfaces at substantially right angles to the plane of the plunger laminations and with said surfaces exposed to the air 7' both inside and out for cooling the same, and

the winding being free of confinement by said frame to allow the heat of the winding to be dissipated without hindrance from the heat de veloped in the frame.

PANFILO TROMBETTA. 

